Many modern vehicles incorporate telematics devices for providing a variety of fee-based subscription services in a mobile environment, including navigational assistance. An in-vehicle telematics device typically includes a plurality of communication interfaces, including cellular and/or satellite transceivers. As part of providing navigational assistance, for example when requesting and receiving road network data, a telematics device may establish a radio communication link with a call center via a wireless (e.g., cellular) network.
Typically, with a telematics system, a driver wanting navigational assistance establishes communication with an operator and tells the operator where he or she wants to go and provides any criteria about how he or she would like to get there. For example, the driver can tell the operator that he or she wishes to drive to a particular city, but by taking a scenic route instead of the most direct route or the fastest route. With this information, the operator instructs a telematics unit of the driver's vehicle to contact a navigation server, which will provide a route to the telematics unit according to the criteria. The telematics unit then gives turn-by-turn instructions to the driver on how to reach the destination according to the requested criteria.
Sometimes drivers wish to reach their destination with particular criteria such that the criteria for distinct portions of a route are not uniform. For example, a driver wanting a scenic route may not want simply the scenic route from one location to another, but may want to drive a further distance to a different scenic route to get the final destination. For instance, a scenic route from one destination to another may be through the mountains, but a driver may wish not to drive through the mountains, but to drive along the coast. Therefore the driver may want the quickest route to the coast, and then proceed along the coast as far as possible in order to reach his or her destination. As another example, in case of an emergency situation, a driver may want the quickest route to a particular evacuation route instead of a route specified as an evacuation route from the driver's current location.
Generally, navigation systems provide routes where each complete route is based on criteria applying to the complete route, but do not provide routes where different portions of a route may have differing criteria. Therefore, if a driver, for example, wants different portions of a complete route to have different criteria, he or she must establish communication with the operator in order to request a new portion of the route after each portion is completed. For example, if a driver wants to get to the coast as quickly as possible and then drive along the coast to his or her destination, he or she must request a route to the coast from the operator who will provide the quickest route to the coast. Upon reaching the coast, the driver must contact the operator again to request a scenic route from the driver's current location to his or her destination.